1. Field of the Invention
The present invention relates to a switching facility for crossed paths provided in a crossing area where the first path and the second path cross each other for switching between a first switching state in which an article transport vehicle is caused to pass through the crossing area along the first path and a second switching state in which the article transport vehicle is caused to pass through the crossing area along the second path.
2. Description of the Related Art
In the switching facility for crossed paths described above, the article transport vehicle can pass through the crossing portion along the first path and the second path by switching the switching means to the first switching state when the article transport vehicle passes through the crossing portion along the first path, and by switching the switching means to the second switching state when the article transport vehicle passes through the crossing portion along the second path.
One conventional switching facility for crossed paths has a diverging crossing portion in which a primary path diverges into a first path and a second path. In this conventional facility, a guide rail for guiding a guided roller provided to an upper portion of the article transport vehicle, and a travel rail for guiding and supporting the travel wheels provided to a lower portion of the article transport vehicle are provided in each of an entrance portion of the primary path which is continues with the crossing portion, a first exit portion of the first path which is continuous with the crossing portion, and a second exit portion of the second path which is continuous with the crossing portion. In the crossing portion, a switchable guide rail is provided that can be switched between a first guiding position in which the switchable guide rail is continuous with the guide rails provided in the entrance portion and the first exit portion and a second guiding position in which the switchable guide rail is continuous with the guide rails provided in the entrance portion and the second exit portion and a switchable travel rail is provided that can be switched between a first travel position in which the switchable travel rail is continuous with the travel rails provided in the entrance portion and the first exit portion and a second travel position in which the switchable travel rail is continuous with the travel rails provided in the entrance portion and the second exit portion. And a switching means is provided with a switching actuator (for example, electric motor etc.). By actuating the switching actuator, the switching means can be switched into a first switching state in which the switchable travel rail is switched to the first travel position, and the switchable guide rail is switched to the first guiding position, and into a second switching state in which the switchable travel rail is switched to the second travel position, and the switchable guide rail is switched to the second guiding position (see, for example, JP publication No. H9-323644 (the patent document 1)).
And another conventional switching facility for crossed paths has a perpendicular crossing portion in which the first path and the second path cross each other perpendicularly. This conventional switching facility includes travel rails for guiding and supporting travel wheels in each of the first entrance portion (of the first path) which is continuous with the crossing portion, the first exit area (of the first path) which is continuous with the crossing portion, the second entrance portion (of the second path) which is continuous with the crossing portion, and the second exit portion (of the second path) which is continuous with the crossing portion. A rotatable travel rail is provided in the crossing portion and is rotatable about a vertical axis between a first travel position in which the rotatable travel rail is continuous with the travel rails provided in the first entrance portion and the first exit portion, and a second travel position in which the rotatable travel rail is continuous with the travel rails provided in the second entrance portion and the second exit portion. And switching means includes first rotation operation means that is pushed by the article transport vehicle as the article transport vehicle advances into the crossing portion to rotate the rotatable travel rail from the second travel position to the first travel position, and second rotation operation means that is pushed by the article transport vehicle as the article transport vehicle advances into the crossing portion to rotate the rotatable travel rail from the first travel position to the second travel position. First rotation operation means and second rotation operation means are provided to the crossing portion. The first rotation operation means rotates the rotatable travel rail to the first travel position to achieve a first switching state, and the second rotation operation means rotates the rotatable travel rail to the second travel position to achieve a second switching state. With each of the first rotation operation means and the second rotation operation means, as the vehicle advances into the crossing portion, the rotatable travel rail starts to be pushed by the article transport vehicle and an urging spring is compressed by the rotation of the rotatable travel rail. And when the article transport vehicle stops pushing, the rotation of the rotatable travel rail is continued by the urging force from the compressed urging spring to switch the travel position of the rotatable travel rail (see, for example, JP Publication No. H03-32602 (the patent document 2)).
In the facility described in the patent document 1, since a guide switching rail is provided in the crossing portion in addition to the travel switching rail, in addition to the fact that the travel wheels of the article transport vehicle are guided and supported by the travel switching rail, a guided roller provided to an upper portion of the article transport vehicle is also guided when the article transport vehicle passes through the crossing portion, ensuring a stable travel of the article transport vehicle, and smooth passage of the article transport vehicle through the crossing portion.
However, the facility described in the patent document 1 requires a switching actuator in the crossing portion for switching the travel switching rail between the first travel position and the second travel position. This tends to make the facility more complex because of, among other things, the wiring work for supplying electric power to the switching actuator, and because of the need to secure installation space for the switching actuator. And, in the facility which has a number of crossing portions, the switching actuator needs to be provided in each of the plurality of crossing portions, which tends to raise the cost of the facility.
In the facility described in the patent document 2, since the rotatable travel rail can be switched between the first travel position and the second travel position as the article transport vehicle advances into the crossing portion, there is no need to provide a switching actuator in the crossing portion for switching the rotatable travel rail between the first travel position and the second travel position. Therefore, compared with the facility described in the patent document 1, the configuration of the facility described in the patent document 2 can be simplified, and a reduction in cost etc. may be expected in the facility with a number of crossing portions.
However, in the facility described in the patent document 2, since only the rotatable travel rail is provided in the crossing portion, only the travel wheels of the article transport vehicle are guided and supported by the rotatable travel rail when the article transport vehicle passes through the crossing portion. This makes it more difficult to ensure stable travel of the article transport vehicle and smooth passage of the article transport vehicle through the crossing portion. And, since the rotatable travel rail is switched between the first travel position and the second travel position as the article transport vehicle advances into the crossing portion, a crossing portion requires both a first rotation operation means and a second rotation operation means, leading to a larger installation space and a more complex configuration of the facility.
Incidentally, in the facility described in the patent documents 2, in addition to the rotatable travel rail, it is conceivable to provide a crossing portion with a rotatable guide rail for guiding the guided roller provided, for example, in the upper portion of the article transport vehicle, such that the rotatable guide rail is rotatable about a vertical axis between a first guiding position in which the rotatable guide rail is continuous with the guide rails provided in a first entrance area and a first exit area, and a second guiding position in which the rotatable guide rail is continuous with the guide rails provided in a second entrance area and a second exit area. In this case, in order to switch the rotatable guide rail between the first guiding position and the second guiding position as the article transport vehicle advances into the crossing portion, two additional operation means must be installed in the crossing portion in addition to the first rotation operation means and the second rotation operation means, leading to a more complex configuration of the facility.